The importance of end-capping or terminating certain aromatic polymers such as, for example, polycarbonates, copolyester-carbonates, polyesters, phenolics, polyphenylene ethers, and the like, with certain end or terminal groups is well known. These aromatic polymers which are not end-capped are in general not sufficiently thermally stable since the free phenolic hydroxyl end groups present in these polymers provide reactive sites which are usually detrimental to the stability of the polymers. Known end-capping agents include the phenolic compounds such as phenol itself, p-tertiarybutyl phenol, and chroman-I.
The prior art further discloses other types of compounds that function as effective end-capping agents for certain of these aromatic polymers such as polycarbonates. These end-capping agents include the alkanol amines disclosed in U.S. Pat. No. 3,085,922; the imides disclosed in U.S. Pat. No. 3,399,172; aniline and methyl aniline as disclosed in U.S. Pat. No. 3,275,601; and the primary and secondary amines as disclosed in U.S. Pat. No. 4,001,184. Other end-capping agents include the aromatic amines disclosed in U.S. Pat. No. 3,028,365; and the ammonium compounds, amonia, primary cycloalkyl amines, and primary aliphatic or aralkyl amines as disclosed in U.S. Pat. No. 4,111,910.
However, according to Schnell, Chemistry and Physics of Polycarbonates (1964), Interscience Publishers, New York, N.Y., page 183, ammonium hydroxide and amines saponify polycarbonates back to the monomers. This is supported by Bolgiano, U.S. Pat. No. 3,223,678, which discloses that small amounts of amines such as monoethanolamine and morpholine break or degrade polycarbonates into lower molecular weight polycarbonates. Thus, this area of chemistry is generally not fully understood and is one where the empirical approach is still generally the method used to determine whether a particular compound or class of compounds will function as effective terminal groups or end-capping agents for the aromatic polymers. This area is further complicated by the fact that even though a particular compound may function as a terminal group for these aromatic polymers, its presence in the polymer chain may adversely affect the advantageous mechanical properties of the polymer.